Arm resonance

vince666 said:
central core of inertia.
Click to expand...

anyways... happened to study something about the central core of inertia into a M.E. matter named "scienza delle costruzioni" (literal translation: "building's science")... not the easiest matter, actually!
some time later, in year 1999, upon my dad's request of solving a problem related to the central core of inertia and finding an algorithm to calculate it at whatever angle via a direct formula (while it was usually found at whatever angle via a complex graphical way with its own inherent lack of precision and the obvious impossibility to calculate it directly and automatically via a direct formula) , I happened to find not just a (complex) algorithm but directly a small formula which worked... and it happened to be a brand new formula (didn't find it in any books) which automatically translated to a small theorem and a new/simplier graphical way of finding it, which didn't require anymore to draw the central ellipse of inertia...
So, very excited from this result I had got as a student I was back then, I went visiting my teacher while showing him what I had found out myself and he simply replied that it was "a useless mental trip"... but WTF? :rolleyes:
My dad didn't think it was a useless mental trip nor did I.
 
Jim, getting properly into weeds is a part of the problem. By digging deeper it turns out that you need a MIT degree just to prove that you don't. Go figure.

My last attempt to clear VTF Earth/Moon...

Balancing scale principle.JPG

Let's say:
- the green force is our balancing mass 1.25g x gravitational accelearation
- the blue force is our VTF
- the levers a and b have the same lenght in our case (talking BB's scale, not the arm, although the same principle applies)
- the green and the blue force are identical for the system to be balanced.

F-green = mg = VTF
m = 1.25g
g-Earth = approx. 9.81m/s^2
g-Moon = approx. 1/6g-Earth = approx. 1.64m/s^2

VTF-Earth = 1.25g x 9.81m/s^2 = 12.26 mN
VTF-Moon = 1.25g x 1.64 m/s^2 = 2,05 mN

Now I'm done.

Rookie :p, I'm considering starting a new thread about choosin/matching a cartridge to a toneram. I just need to articulate the intro and this will take some time...and a serious amount of English lessons on my part.
 
i think you just gave the right reply before, Borut, without needing the latest.

it's a balancing system.
if VTF is set to zero so that the system is balanced and the arm stays horizontal (without even touching the record), then being on earth or on the moon won't change the balanced situation and VTF will still be zero.
If you unbalance it on one side to give some VTF then the gravity difference between earth and moon must be taken into consideration.
As simple as that, and you just had got this right before. ;) (but it was funny to let you going mad on this a bit, after all :toothy8: )

anyways, regarding the (negligible) effect of the air as a fluid, as just talked before, we should also consider the atmosphere difference between earth and moon. LOL :p:oops:
 
Last edited:
The speed of the arm and cartridge body in the fluid is low, and the surface area of the cantilever is low, such that neither would be significantly impacted by the fluid (air).

That said, operating the table in a vacuum chamber should eliminate all atmospheric influence (vibrations in the air) and only leave feedback (sympathetically vibrating record, excited by playing the program material) and mechanical (motor and bearing- direct coupled vibrating elements that can transfer through connected solids).

Chew on that a while.
 
You must log in or register to reply here.
Back
Top